Declan L. Goode (1), Hilde H. Wijngaard (1), and Elke K. Arendt (2). 1.
Department of Food and Nutritional Sciences, Bio-Transfer Unit, National
University of Ireland, University College Cork, Ireland. 2. Department of Food
and Nutritional Sciences, National University of Ireland, University College
Cork, Ireland.

Abstract
This paper reports on the effects that the addition of both malted barley and
commercial enzymes (Bacillus spp.) has on the processability and quality
of worts when brewing with inclusions of raw barley. Increased inclusion of
malted barley resulted in increases in extract recovery levels, wort alpha-amino
nitrogen levels, and fermentability and in decreases in wort viscosity and
beta-glucan levels. While increases in wort amino acid levels resulted from
inclusions of high levels of malt, the endogenous malt enzymes were found to
exhibit very poor raw barley protein-hydrolyzing ability. Likewise, the
endogenous malt amylases were found to exhibit very poor raw barley
starch-hydrolyzing ability. As the level of malt was increased, its raw barley
hydrolytic effects decreased. When mashing with 100% raw barley substrate and
commercial enzymes, exogenous protease (B. subtilis) additions yielded
increases in total soluble nitrogen levels, alpha-amino nitrogen levels, wort
color, and extract recovery levels. However, the protease efficiency decreased
as the level of protease was increased. Exogenous beta-glucanase (B. subtilis)
had little impact on mash filtration, but it reduced high-molecular-weight wort
beta-glucan levels. Exogenous alpha-amylase (B. subtilis) was found to
have the greatest positive impact on mash separation. Likewise, exogenous
alpha-amylase level increases resulted in higher wort glucose and maltotriose
levels and lower maltose levels. Optimal addition of an exogenous high-heat
thermostable alpha-amylase (B. licheniformis) in combination with the
exogenous alpha-amylase (B. subtilis) was found to be necessary for
complete starch conversion and maximum extract recovery from the raw barley
substrate.
Keywords: adjunct, barley, commercial enzymes, enzymes, mashing, wort
quality